To optimize a load for each of facilities when a specific work process for production processes is executed by using a plurality of the facilities based on the latest production plan regardless of a difference of product types.

The load simulator comprises: a database 10 for storing the number of products to be produced, which is scheduled for each type of products to be manufactured within a predetermined period of time; a tact time database 11 for storing a tact time required for each of the facilities to execute the specific work process for each product unit of the product types; a specifying means 2 for specifying the facilities to execute the specific work process for each product type; a load calculation unit 1 for calculating the load for each of the facilities based on the number of the products to be produced and the tact time, when the specific work process is implemented according to a relation between the product types specified by the means 2 and the facilities; and a notification means 3 for informing a system user of the load for each of the facilities, which is calculated by the load calculation unit 1 for calculating the load for each of the facilities.